Executing
import numpy as np
t1 = np.arange(1,10)
t2 = np.arange(11,20)
t3 = np.concatenate((t1,t2),axis=1)
results in a
Traceback (most recent call last):
File "<ipython-input-264-85078aa26398>", line 1, in <module>
t3 = np.concatenate((t1,t2),axis=1)
IndexError: axis 1 out of bounds [0, 1)
why does it report that axis 1 is out of bounds?
Your title explains it - a 1d array does not have a 2nd axis!
But having said that, on my system as on @Oliver W.
s, it does not produce an error
In [655]: np.concatenate((t1,t2),axis=1)
Out[655]:
array([ 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 17, 18,
19])
This is the result I would have expected from axis=0
:
In [656]: np.concatenate((t1,t2),axis=0)
Out[656]:
array([ 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 17, 18,
19])
It looks like concatenate
ignores the axis
parameter when the arrays are 1d. I don't know if this is something new in my 1.9 version, or something old.
For more control consider using the vstack
and hstack
wrappers that expand array dimensions if needed:
In [657]: np.hstack((t1,t2))
Out[657]:
array([ 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 17, 18,
19])
In [658]: np.vstack((t1,t2))
Out[658]:
array([[ 1, 2, 3, 4, 5, 6, 7, 8, 9],
[11, 12, 13, 14, 15, 16, 17, 18, 19]])